At this age, your child is ready for primary school now. He probably already knows and are used to pre-school activities and procedures. Though your child knows the routines it would still be a little difficult for him to get used to it.
What you need to know:
A regular school has a different environment for your kid in many ways. He will now have to stay longer (not probably in the starting months), be more attentive, follow routines, which were not so stringent in pre-school, sitting for longer hours with no roaming around, making different friends etc. So, it is required that you prepare him for coping to this different environment gradually, but well in advance.